1. Field of the Invention
The present invention relates to a method for forming a film.
2. Description of the Prior Art
Films have been heretofore deposited by various processes such as CVD (chemical vapor deposition), sputtering, MBE (molecular beam epitaxy), and the like. In plasma enhanced CVD (referred to simply hereinafter as plasma CVD), the use of high frequency excitation, microwave excitation, hybrid resonance and the like has been developed. Particularly in the plasma CVD process which utilizes a resonance with a magnetic field (referred to as "plasma CVD in magnetic field", hereinafter), the development thereof has actively taken place and, because of its high film deposition efficiency which results from the use of a high density plasma, its diversification in application has been expected. In the practical film deposition in the presence of a magnetic field, however, a difficulty has been encountered to deposit uniform films on an irregular surface without being influenced by such surface irregularity. This difficulty has hindered practical progress of the microwave CVD in magnetic field in the industries. The fact that a plasma CVD in magnetic field consumes an enormous amount of energy at its operation also is a bar to its gaining popularity in the industrial field. A diamond-like carbon (DLC) film can be uniformly deposited on a substrate as large as 10 cm or more in diameter by the use of microwave plasma CVD in magnetic field. In the deposition of such DLC films by this process, the diamond nuclei formed in the vapor phase are trapped on the substrate upon their contact with the substrate. Thus, the DLC film grows spread in a tapered form from each nucleus, and results in a film having poor adhesion with the substrate. Furthermore, since the diamond crystals grow in a tapered form from a diamond nucleus center trapped on the substrate, a compression stress accumulates around the grain boundaries within the DLC film. The poor adhesion of the film with the substrate and the compression stress within the film have constituted a hindrance to the practical use of DLC films.